The present invention relates to an electric lamp and more particularly relates to incandescent bulbs for use in the automotive field, especially in headlights.
From International Patent Disclosure WO 99/28949, an electric lamp is already known that is suitable for use both as a turn indicator or brake light in the tail region and as a turn indicator in the front headlight. The lamp uses a base of plastic with fastening tabs integrally formed on in a V, which form a receptacle for a peglike socket or plug part.
A further refinement of this lamp is described in German Patent Application DE-PA 198 43 506. The base has two resilient tabs, each provided with a detent protrusion, and a fastening ring supported rotatably about the annular axis of the base.
It is the object of the present invention to furnish an electric lamp that creates a simple connection which can easily be undone again, and that functions reliably over a long service life. It is a further object of the invention to furnish an electric lamp with an improved lamp base that enables simple mounting of the lamp in the lamp socket.
Initial attempts to make the entire lamp base out of plastic have not proven themselves, because the effect of a plastic detent mechanism decreases over time. This detent mechanism has therefore been improved with the aid of a metal spring. In a first embodiment, a spring wire bent into a clip is advantageously used; the ends of the wire are let into the plastic wall of the base. In a further especially preferred embodiment, a sheet-metal spring embodied as a stamped and bent part is used.
The electric lamp according to the invention has a luminous filament (incandescent body or discharge arc) that is surrounded by a lamp bulb, and also has a lamp base in which the bulb is secured, as well as electrical base contacts and power supply leads for supplying power to the luminous filament.
The base comprises a frustoconical upper part, which surrounds the lamp bottom (typically embodied as a pinch), and a lower part secured to it, which protrudes partly past the circumference of the upper part and which in the region of the protruding portion has two detent mechanisms for fastening in the reflector.
The detent mechanisms each comprise a detent protrusion located on the outside and facing inward, which is an integral component of the lower part and a metal spring located opposite the detent protrusion and cooperating with it and secured in the lower part, the metal spring being suitable for locking in detent fashion in a recess on the reflector, while the detent protrusion is suitable for unlocking this locking of the metal spring again.
The above characteristics make simple mounting of the lamp in a reflector with a neck (or some other fastening means) possible. The locking can be undone again easily and reliably. The lamp is thrust into the reflector as far as the reference plane. After that, still further force must be exerted on the two protruding portions of the base, in order to deform the springs and bring about the locking in recesses of the reflector neck. As a result, force that keeps the lamp in the reflector always prevails at the spring.
In addition, the base on its underside advantageously has a recess for receiving a peglike socket part or plug part. As a result, the lamp of the invention is suitable for mounting on a lamp socket embodied as a plug.
In detail, the present invention relates to an electric lamp, which defines an axis A, having a bulb which contains a luminous filament, and having a base in which the bulb is fixed, the base being provided with external contacts, and having at least two power supply leads which electrically conductively connect the luminous filament to the contacts. The base is subdivided into an upper part, which retains the bulb an essentially circular cylindrical, and a lower part for external fastening, and the lower part protrudes past the upper part and the protruding portion is embodied as a detent mechanism for the external fastening. The detent mechanism in each case comprises a detent protrusion located on the outside and facing inward, which is an integral component of the lower part, and a metal spring located opposite the detent protrusion and cooperating with it and secured in the lower part. The metal spring is suitable for locking in detent fashion in a recess on the reflector, while the detent protrusion is suitable for unlocking this locking of the metal spring again.
The detent protrusion advantageously has a radially inward-pointing projection, which is connected to a base part via two chamfers.
In an especially preferred embodiment, the metal spring comprises a retainer element connected to the lower part of the base via an anchoring means and a spring part formed of two legs, and the retainer element is at least in part located approximately in the plane transverse to the lamp axis. A first, short leg is integrally formed onto the retainer element, and a second, long leg is attached at an acute angle to the free end of the first leg in such a way that it extends approximately parallel to the lamp axis.
In particular, an outward-pointing (away from the axis) projection, located approximately opposite the projection of the detent protrusion, is seated on the free end of the second leg, so that the unlocking is done by pressing the projection of the outer detent protrusion into the recess in which the projection of the second leg is seated.
In a first embodiment of the invention, the metal spring is embodied as a sheet-metal spring part, with a flat base plate transverse to the lamp axis as a retainer element and with a spring part formed in the shape of a V of two legs, and a first, short leg is attached to the base plate and is inclined relative to the base plate. A second, long leg is attached at an acute angle to the first leg and penetrates the plane of the base plate in such a way that it is again oriented approximately parallel to the lamp axis. The anchoring means may be realized by means of bores in the base plate.
In a second embodiment of the invention, the metal spring is embodied as a spring wire piece, and the retainer element has a base part approximately transverse to the lamp axis and the anchoring part is an extension of the base part, which is attached to the base part and is oriented parallel to the lamp axis, and the short leg is bent backward on the base part by more than 120xc2x0, in particular by approximately 180xc2x0. Preferably, the long leg is attached laterally to the short leg, in particular with an offset bend. This has the advantage that the spring travel distance is lengthened, and furthermore a stabilizing part between symmetrical first legs can be better secured.
Very good results with economical use of material are attained with an embodiment in which the spring wire piece is constructed symmetrically of two halves, both long legs of which are connected to one another via a connecting piece that forms the projection. An especially reliable locking is attained in that the connecting piece has a curved piece bent backward toward the second legs.
The functional safety and reliability is further enhanced by the provision that the two first legs of the symmetrical spring wire piece are connected to one another via a stabilizing part.